Progressive bilateral lipoma arborescens of the knee complicated by juvenile spondyloarthropathy: a case report and review of the literature

Objectives: To report an unusual case of lipoma aborescens (LA) presented in a patient with treatment-responsive juvenile spondyloarthropathy (JSPA) and to summarize the clinical manifestations, therapy and prognosis of LA by literature review.

Methods: We report an atypical case of a 17-year-old patient with an initial presentation of juvenile spondyloarthropathy, whose inflammatory condition was improved successfully by traditional anti-rheumatic drugs and an anti-TNF alpha agent but developed progressive swelling of bilateral knees. Lipoma arborescens were diagnosed in each knee by synovial biopsy obtained by arthroscopic surgery. Fifty-one cases of LA have been reported and are reviewed in detail.

Results: Clinically, LA could present as monoarthritis or oligoarthritis. The lateral compartment of the knee is the most common site of involvement. Several cases were reported as a comorbidity of inflammatory diseases, but were not improved by anti-inflammatory therapy. Most patients were diagnosed by classic MRI and biopsy findings. The lesions can be managed by open or arthroscopic surgery, but a minority of the cases may have reoccurrence in the same or opposite joint.

Conclusions: LA is a very rare lesion of the synovial and bursal tissue with an unknown etiology. It is considered to be a benign proliferation of the synovial fat associated with trauma, degenerative or inflammatory conditions. LA should be considered as a secondary or comorbid condition in inflammatory arthropathies if other joints respond well to intensive therapy and one or more do not.